Antistatic carpet construction

ABSTRACT

A CARPET IS DESCRIBED HAVING DURABLE ANTISTATIC PROPERTIES WHICH ARE OBTAINED BY INCORPORATING ELECTRICALLY CONDUCTIVE FIBERS IN A NONWOVEN WEB WHICH GOES TO MAKE UP AN INTEGRAL PART OF THE CARPET CONSTRUCTION. METHODS OF FORMING THE CARPET ARE DESCRIBED WHEREBY THE NONWOVEN   WEB CONTAINING ELECTRICALLY CONDUCTIVE FIBER IS INCORPORATED IN THE TUFTED CARPET STRUCTURE.   D R A W I N G

April 23, 1974 w R BRINKHQFF ETAL 3,806,401

ANI'IISTATIC CARPET cons'rnuc'rmu Filed April 5. 1972 PER CENTMETALLIZED FIBER United States Patent 3,806,401 ANTISTATIC CARPETCONSTRUCTION William R. Brinkhofi, and Edward R. Frederick, Pittsburgh,Pa., assignors to Armstrong Cork Company, Lancaster, Pa.

Filed Apr. 3, 1972, Ser. No. 240,708 Int. Cl. D04h 11/00, 11/08 US. Cl.161-67 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTIONField of the invention This invention relates to a tufted carpetconstruction and, more particularly, to a carpet having durableantistatic properties.

Description of the prior art Antistatic carpets are available, forexample, one of which incorporates in the tufting yarn a small quantityof a continuous filament of a stainless steel fiber, and another inwhich the tufting yarn is made up of a combination of staplenonconducting fibers and a small portion of conductive stainless steelfibers. It is also known to use small quantities of other types of metalfibers in forming tufting yarns to achieve in the tufting yarn aconductive characteristic such that, in carpets utilizing such tuftingyarn, especially under low humidity conditions, the propensity forbuilding up a static charge is minimized by dissipating such staticcharges by means of the electrically conductive filaments. It is alsoknown from US. Pat. No. 2,302,003 to provide a carpet having a flexible,electrically conductive material adhered to at least a portion of theunderside of the carpet and a plurality of electrically conductiveelements of textile material and electrically conductive rubbercomposition contacting said coating and extending to substantially thetop of the carpet to dissipate static charges. It is also known from US.Pat. No. 3,582,445 to construct a carpet containing a minor percentageby weight of an electrically conductive fiber in its surface structure(i.e., tufts) in which the electrically conductive fiber may be asubstrate of a conventional fiber such as nylon, polyester, acrylic,etc., having formed on the surface an electrically conductive coatingfrom, by way of example, a polymeric binder solution or emulsion whichcontains dispersed therein finely divided metals such as silver gold,platinum, brass, nickel, aluminum, tungsten, etc., or other finelydivided electrically conductive materials such as copper oxide or carbonblack or alternatively a chemically plated conductive coating of metalsuch as nickel, copper, cobalt, chromium, zinc, tin or other which maybe formed by means such as vacuum evaporation of the metal on thefibers.

SUMMARY OF THE INVENTION We have now found that a tufted carpet havingdurable antistatic properties may be formed by forming a novelconstruction in which a web containing a portion of electricallyconductive fibers is needle-punched to a dimensionally stable primaryscrim backing after which conventional nonconductive tufting yarns aretufted through the backing and web to form a conventional carpet. Thetufts are then preferably locked into the backing by means of aconventional latex adhesive, and the tufts may be either left in theirloop form or may be sheared to give a shag or cut pile configuration.Alternatively, the tufted carpet may be formed by initially tuftingconventional nonconductive tufting yarns through a dimensionally stableprimary scrim backing and a web containing a portion of electricallyconductive fibers needle punched thereto. The needle-punched nonwovenweb having the electrically conductive fibers incorporated thereinserves or functions to form a layer in the interior of the carpetwhereby static charges built up, for example, under low humidityconditions by traffic trically conductive fibers in the nonwoven web issuch that a continuous electrically conductive circuit is notestablished.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, FIG. I is a simplifieddiagrammatic representation of an enlarged cross section of a tuftedcarpet structure formed in accordance with the invention; and

FIG. II is a graph representing the static dissipating effectiveness ofthe carpet construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. I of thedrawing, the antistatic carpet construction comprises a dimensionallystable scrim 3 and a layer of staple fibers 4, a portion of which carryan electrically conductive coating on the surface thereof. The layer ofstaple fibers has been needled into the scrim to provide an electricalyconductive layer of fibers 4 with the nonconductive yarn 6 tuftedthrough the scrim and the electrically conductive needled layer toprovide a tufted surface supported by the scrim with the tufts being incontact with the electrically conductive needled layer 4. In order tolock the tufts into position, a conventional latex adhesive layer 7 wasapplied to the backing.

The dimensionally stable scrim may be any of the conventional type suchas a weave of polypropylene filaments or ribbon, jute or burlap or otherwoven or nonwoven scrims. In accordance with well-known procedure, aconventional lapper may be used to deposit on the surface of the scrim auniform web or mat of garneted staple fibers. These staple fiberscomprise a mixture of nonconductive fibers and electrically conductivefibers such as fibers having an electrically conductive metallic coatingor fine metal fibers mixed with conventional nonconductive fibers suchas nylon or acrylic fibers. The product is then passed through aconventional needle loom which acts to needle the fibers into a layerbonded to the scrim, the needles serving to compact the web andintertwine fibers therein through the scrim and bond the Web thereto.After needle bonding, the product passes through a conventional tufter,which tufts yarn through the scrim and the conductive layer to develop aface comprising tufts which extend above the needled nonwoven web layer.The tufting yarn may be made up of any suitable nonconductive fibermaterial such as nylon and may be either a conventional continuousfilament yarn or a yarn spun from staple fibers. The tufts may be of theloop type illustrated in FIG. I or they may be cut to provide a cut piletype carpet structure. After tufting, the carpet may be dyed or printedif desired, and a conventional rubber latex adhesive material is usuallyapplied to the back of the carpet to lock the tufts in 7 position,

Alternatively, a tufted scrim structure may have a nonwoven web appliedto the back thereto and bonded to the structure by needle punchingthrough the backing, bringing the fibers of the nonwoven web through thescrim and into the tufts to form a carpet structure similar to thatdescribed in US. Pat. No. 2,706,324. In any event, the layer of staplefibers, a portion of which carry an elecelectrically conductive finemetallic fibers, provide an electrically conductive layer such thatcharges built up in the nonconductive fibers in the tufts are readilydissipated by contact with the electrically conductive fibers in theneedled layer.

The following examples will serve to more fully illustrate theinvention.

Two series of antistatic carpet structures were made up as follows:

A series of 2 oz. per square yard nonwoven webs were prepared fromintimate mixtures of metallized 3" 2.5 denier per filament stapleacrylic fibers and 3" 15 denier per filament nylon staple fibers. Foreach carpet structure, a 2 oz, nonwoven web was first needle bonded to adimensionally stable woven polypropylene primary scrim after which nylonyarn was tufted through the needle bonded web and scrim. In Series A, aneedle depth of /2" with 225 penetrations per inch was used to needlebond metallized fibers in the web of tufted nylon carpet improves thestatic control quality of the carpet with the greatest change ingenerated charge level taking place from the control to a 5% of webweight metallized fiber content with improvements beyond a to of webweight of metallized fiber content being slight. Increases in depth ofneedle penetration and number of penetrations per unit area for the samepile height do not seem to produce any significant improvement in staticcontrol quality. However, decrease in pile height from /2" to A" whilemaintaining the other construction parameters constant produces animprovement in static control quality. Scouring a 20% metallized fibercontent carpet sample did not appear to produce any change in generatedstatic charge level compared to a nonscoured sample. Trafiic exposurewith no subsequent scouring of a 20% metallized fiber content carpetresulted in a lowering of the generated static charge level.

The graph set forth in FIG. II of the drawing shows the web to thescrim, and in Series B a needle depth of 60 the Voltage generated 011FWD Subjects Versus the Percent with 300 penetrations per inch wasutilized. To finish the carpet construction and to lock in the tufts, 24to 28 ounces of latex per square yard were applied to the back of thecarpet and a 7 oz. woven burlap secondary backing adhered thereto, thecarpet being passed through an oven to cure and set the latex.

In Table I which follows, the details of Series A and Series B carpetconstructions are set forth:

(based on web weight) of 2.5 d.p.f. metallized acrylic fiber in A seriesexperimental carpet structures. The voltage was generated by the shutflewith the feet being lifted from the carpet at end of each strokeutilizing leather soles and rubber heels against the carpet surface,curve A represents voltages on subject 1 and curve B represents voltageson subject 2, the percent metallized fiber in the carpet structure beingplotted against the peak voltage in kilovolts.

1 Sample B-l has pile height of M.

The carpet structures of Series A and B were subjected to staticpropensity tests, evaluations being made in accordance with a modifiedCRI (Carpet and Rug Institute) charge propensity test in which anenergetic shufile was used for charged generation. Samples were firstconditioned for a minimum of three days at 20% relative humidity and at75 F. prior to charge measurement. The maximum charge accumulated on asubject sample, wearing test shoes with leather soles and rubber heels,-during a one-minute shufile, was recorded, in terms of a voltage, as acharacterization of the static charge property of the sample tested.

The construction parameters of the Series A and Series B carpet samplesare as follows. In the A series of samples, a series of samplescontaining 0, 5, 10, 20 and 50%, respectively, of 2.5 d.p.f. metallizedacrylic fibers based on the 2 oz. web were used. In Series B, the firstsample was the same as the 50% level utilized in Series A, but a needledepth penetration with 300 penetrations per square inch was utilized,and a control sample containing no metallized fibers was also tested.The following results in Table II are of the measurements on carpetsamples in Series A and B.

It appears from the data gathered that the inclusion of What is claimedis:

1. An antistatic carpet construction comprising a dimensionally stablescrim, a nonwoven layer of staple fibers, of which at least about 5% byweight of the nonwoven layer is of electrically conductive fibers withthe maximum percentage of said electrically conductive fibers in thenonwoven layer being insufiicient to establish a continuous electricallyconductive circuit, said nonwoven layer being needled into the scrim,and nonconductive' yarn tufted through the scrim in contact with theelectrically conductive needled layer to provide a tufted surfacesupported by the scrim with the tufts in contact with the electricallyconductive needled layer.

2. An antistatic carpet construction in accordance with claim 1 in whichthe electrically conductive fibers carry a conductive coating on thesurface thereof.

- 3. An antistatic carpet construction in accordance with claim 2wherein at least some of the tufts are sheared to give a cut pileappearance.

MARION E. MCCAMISH, Primary Examiner US. Cl. X.R. 161-62, 63,

Patent No. 3,8O6. +O1 Dated April 23, 97

lnventor(s) William R. Brinkhoff and Edward R. Frederick It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the specification, column 1, line 56, the words "silver gold" shouldread --silver, gold--.

Column 2, line 11, after the word "traffic" the remainder of theparagraph should read --thereover, are dissipated and yet the percentageof electrically conductive fibers in the nonwoven web is such that acontinuous electrically conductive circuit is not established.-

Column 2, line 31, "electricaly should read electrically- Signed andsealed this 5th day of November 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM Po-10 0 USCOMM-DC 6O376-P69 U.S GOVERNMENT PRINT NG OFFICE:I909 D366334

